Coarse-Grain Simulation of Lubricant Polymer Solutions

Polymer solution is used as lubricant in Tribological applications. Viscosity index improver is used to normalize temperature dependence of viscosity of the lubrication oil. Biological system such as synovial joint is a kind of polymer solution and strongly related to Tribology. Here we show our numerical simulation approach to investigate the dynamics of polymer solution. The numerical scheme is for simulating the dynamics of suspensions of Brownian particles, coupling molecular motion treated by Langevin equation and hydrodynamics treated by lattice Boltzmann method. The motion of polymer segments are simulated under shear condition in bulk, and in confined geometry. The viscosity change due to the change of polymer structure is found both in bulk and in confined geometry. In order to simulate realistic polymers, we modify each polymer segment as polar and non-polar particles. Point dipoles are added on the polar segments. Since the relative permittivity is very different in water and oil condition, the structure of the polymer is strongly affected by the distribution of the polar segments.